Pharmacokinetic disposition and residue status of tilmicosin in broiler chicken after ‘In-crop’ and ‘In-water’ administration

The aim is to study the pharmacokinetics and tissue residue status of tilmicosin after administration through ‘in-crop’ and ‘in-water’ routes and compare the effectiveness of the two routes and establish a suitable dosage regimen for treating Mycoplasma gallisepticum infection in broiler chicken.

The plasma pharmacokinetic disposition of tilmicosin in broiler chicken was investigated after administration orally by direct deposition at crop (25 mg/kg body weight) or drinking water (40 mg/kg b.wt.). Residues of tilmicosin in tissues of broiler chicken were assayed. The plasma and tissue concentrations of tilmicosin were analyzed by reverse-phase high-performance liquid chromatography (HPLC) method. The plasma concentration-time data was described by the non-compartmental model for both routes and pharmacokinetic parameters were calculated. The data were statistically analyzed by Mann-Whitney U test.

The mean plasma concentrations of tilmicosin in two routes tested (in-crop, in-water) were effective above MIC reported for Mycoplasma gallisepticum (0.05 |jg/ml) up to 24 h. In addition, the drug residue in lungs was found at desirable concentration up to 22 days. However, residues of tilmicosin in tissues were above the advocated maximum residue limit (MRL) till 18^th day in muscle and liver and till 22^nd day in kidney. The results of the study indicate that the antimycoplasmal drug tilmicosin can be therapeutically efficacious after administration in crop as well as in drinking water.